ES2379701T3 - Rotary impulse sealant - Google Patents

Abstract

The invention is a transverse rotary impulse sealer for heat sealing heat sealable materials that includes a heating zone for sealing the material and a cooling zone for supporting the newly formed seal. The device comprises a conductive zone and a resistive zone that are in electrical communication. The resistive zone comprises a cylindrical member having a circumferential band of resistive material disposed on its surface. The conductive zone comprises a cylindrical member having a plurality of conductive strips extending laterally across its surface that are in electrical communication with the resistive band. Current is applied via a brush to the conductive strips. Current flows from the conductive strips into the resistive band and exits through a conductive strip that is in contact with a ground. Current path through the resistive band defines the heating zone, and the cooling zone is defined by area of the resistant band outside the heating zone.

Description

Rotary impulse sealant

Background of the invention

The invention generally relates to heat seal devices and more particularly to impulse heat seal devices.

Flexible packaging products are used to protect a wide variety of items from both physical abuse and contamination. These packaging products include, for example, plastic bags and small bags that may be useful for packaging items such as food, and buffer materials, such as cellular air material.

Flexible packaging can be prepared from laminate sheets or layers that are joined to form a desired product. The packaging may include thermoplastic materials that can be joined using a heat seal. A heat seal is produced by applying heat to thermoplastic materials until they melt and melt effectively to form a seal. In many circumstances it may be desirable to join two sheets of thermoplastic material to form a constant continuous seal. It can be difficult to use heat to melt together baseless materials to form a constant continuous seal because the materials can melt and stick to the heat element or the seal can separate when the heat element no longer holds it.

A technique for producing a constant continuous seal includes passing the thermoplastic materials that will be cast together on a heated drum. Typically, the entire surface of the drum is heated by means of an inner resistor wire or hot fluid. When materials pass over the surface of the drum, heat melts the layers together. If the newly sealed layers leave the drum still hot, the seal will not have cooled sufficiently to produce a strong bond and the seal may separate or break. As a result, these devices typically require the presence of a Teflon strap between the layers and the drum. The Teflon belt prevents the layer from adhering to the drum and provides additional support to the newly formed seal after it has left the drum.

In another technique, a continuous seal can be made by passing thermoplastic materials between heated rollers. A drawback associated with this method is that the contact time for heat sealing between the rollers is extremely short. Typically, good seals can be made only if the rollers move very slowly or if the materials are preheated before passing through the heated rollers. In addition, the newly formed seal may break or burst if the molten materials are not properly secured after having passed between the rollers.

Impulse sealing is another method commonly used to produce a continuous seal. In a form of impulse sealing, the materials are placed forward between opposite sealing jaws. An electrically resistive material, such as nichrome resistive wire, is placed inside one of the jaws and covered with an electrically insulating layer. Thermoplastic materials are placed forward between the jaws and an electric current passes through the resistive wire to melt the materials. After the power has been turned off, heat transfer from thermoplastic materials to the jaws facilitates faster cooling and solidification of the newly formed seal. The jaws open afterwards and the molten materials are placed forward to produce the next seal. The advantage of this method is that the seal is cooled to get the proper force before the jaws open. The drawback of this system is that it requires more time and that the materials cannot continuously move forward in a perfect way.

Thus, there is still a need to provide a device and method for producing a continuous heat seal on materials that can be heat sealed to provide adequate heating to produce a seal while maintaining the newly formed seal until it is cool properly.

Japanese patent application 48 046673 describes a transverse rotary sealant having two conductive cylindrical members and a rotary cylindrical member disposed therebetween. The resistive member includes a plurality of electrically resistive strips that extend laterally across the surface of the resistive member, and which are in electrical communication with the conductive members.

Brief Summary of the Invention

The invention is a device for making a heat seal that overcomes many of the disadvantages associated with the prior art. The present invention provides a transverse rotary pulse sealant comprising:

a) a first and a second rotating cylindrical conductive member, each having a plurality of electrically conductive strips that extend laterally across the surface of said conductive members; b) a rotating cylindrical resistive member disposed between said first and second conductive member, said resistive member having a heating zone, cooling zone, an insulated surface and a plurality of electrically resistive strips that extend laterally across the surface of said resistive member, wherein said resistive strips are in electrical communication with said first and second conductive member; and c) an electrical contact in electrical communication with said first conductive member and a ground contact in electrical communication with said second conductive member, wherein said heating zone is defined by the current flow from said electrical contact to said earth contact .

The device described below is in the form of a cylindrical roll that has a heating zone set in an adjustable manner to produce a constant continuous seal and a cooling zone.

The electric current is applied to the conductive zone and flows to a corresponding electrically resistive zone that is in electrical communication with the conductive zone. The source of the electric current is normally set in relation to the rotation of the roll so that a "hot zone" is created which does not change with respect to the rotation of the sealant by rotary pulse. The rotary pulse sealant includes an electrical contact and a ground contact that are individually in electrical and mechanical communication with a conductive member. As a result, a current path can be created through which current can flow from the electrical contact through the resistive member and to the resistive member. The current can then flow through the resistive member and out to the conductive member that is in electrical communication with the ground contact. The hot zone is defined by the path of the current through the resistive member. The size of the hot zone can be increased or decreased by changing the position of the electrical contact or the earth contact with respect to each other. The cooling zone is defined by the part of the band that is outside the current path. Changing the size of the hot zone changes the contact time of the material that can be heat sealed with the heating zone, and allows the surface area of the resistive band to be adjusted to achieve optimal conditions for heat heating, the support, and the cooling of materials that can be heat sealed.

The rotary pulse sealant can be used to produce transverse heat seals. In the embodiment described below, an electrically resistive zone is in communication with two electrically conductive zones. The resistive zone comprises a generally cylindrical resistive member having a plurality of electrically resistive strips that extend laterally across its surface. The electrical contact and the earth contact are arranged in separate conductive zones and each is in mechanical and electrical communication with a conductive strip. In this embodiment, the current flows from the electrical contact and to a resistive strip, thereby creating a heating zone that extends laterally through the surface of the resistive member. The current then passes from the resistive strip to the ground contact. The size and quantity of the resistive strips may vary to change the width of the resulting heat seal and the distance between successive heat seals.

Thus, the invention is a rotary pulse sealant that provides a roll or drum having a plurality of zones for holding and cooling heat seals and an individual hot zone on the roll defined by selected activated conductive strips adjacent to the zone. of cooling to create the seals, either longitudinally or transversely.

Brief description of the various views of the drawings

Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and in which:

Figure 1a is a front view of a rotary pulse sealant representing two sheets of material which can be heat sealed by moving over the sealant; Figure 1b is a side view of a rotary pulse sealant shown in Figure 1; Figure 2 is a perspective view of a rotary pulse sealant representing the area of heating created by the flow of current through the resistive zone; Figure 3 is a perspective view of the rotary pulse sealant shown in Figure 1; Figure 4 is an enlarged perspective view of the rotary pulse sealant shown in Figure 3; Figures from 5a to 5c are side views of a rotary pulse sealant in which the conductive member and resistive member are in direct electrical contact with each other; Figure 6 is a side view of a rotary pulse sealant depicting a belt to maintain the pressure on the material that can be heat sealed when moving on the sealant; Y Figure 7 is a perspective view of a rotary pulse sealant that is useful for producing seals. transversal in a material that can be heat sealed.

Detailed description of the invention

The invention will now be described in more detail below with reference to the accompanying drawings, in which some, but not all, embodiments of the invention are shown. In fact, the invention can be carried out in many different ways and should not be construed as limiting the embodiments set forth herein; instead, these embodiments are provided for this disclosure to meet applicable legal requirements. Similar numbers refer to similar elements from the beginning to the end.

The rotary pulse sealants illustrated from FIG. 1 to FIG. 6 are particularly useful for producing a constant continuous heat seal in the direction of the travel machine. The sealants of FIGS. 1-6 are not in accordance with the invention and are given to aid the description of the present invention. The term heat sealable material is used throughout this application to refer to materials that can comprise a tube, layers, sheets, and the like that can be bonded with a heat seal. Such materials include, without limitation, layers and laminates comprising thermoplastic and thermosetting materials, substrates having waxes and adhesives that can be heat sealed, and metallized layers and poly-coated sheets, such as poly-coated aluminum foil, and poly paper -coated, and the like. The rotary pulse sealant is in the form of a rotating roll that has a cooling zone and a heating zone that is stationary with respect to the rotation of the roll. The heat-sealable materials that move on the roll melt together when they pass through the heating zone and the roll keeps them and is allowed to cool on the roll after leaving the heating zone. The roll maintains the newly formed heat seal until the molten material has cooled sufficiently to prevent seal breakage.

With reference to FIG. 1a, the rotary pulse sealant is illustrated and is designated in general terms with the reference number 10. The rotary pulse sealant comprises a generally cylindrical roll having an electrically resistive zone 20 and an electrically conductive zone 25 in electrical communication with each other. The electric current is applied to the conductive zone by means of an electrical contact 30 and flows from the conductive zone to a corresponding section on the electrically resistive zone.

A higher degree of resistance resulting in the production of thermal energy prevents electrical current within the resistive zone. As shown in FIG. 1a, two sheets of material that can be sealed 15 are moving around the sealant by rotating impulse in a face-to-face contact with respect to each other over the heated resistive zone 20 causing the areas of heat-sealable material adjacent to The heated resistive zone melts and melts together. After passing over the heating zone, the surface of the roll in the cooling zone 19 (see FIG. 1b) maintains the newly formed seal until the seal has cooled adequately. FIG. 1b is a perspective view of the rotary pulse sealant 10 illustrating two separate layers of material that move around the roller and that are melting together. As shown in FIG. 1b, the brackets labeled with the reference number 17 illustrate an exemplary heating zone, and the brackets labeled with the reference number 19 represent the cooling zone.

The electrical contact 30 may have the form of a spring-operated contact, which is also commonly referred to as a "brush." Typically, the electrical contact comprises a carbon brush that is disposed in intimate sliding contact with the surface of the conductive zone. The electrical contact is typically in contact with a single conductive strip at a given time. However, it should be recognized that in some embodiments it may be desirable to have an electrical contact that contacts multiple conductive strips simultaneously. Other methods for providing electric current include induction transfer such as through an inductive coil system, and radiation transmission.

The rotary pulse sealant may also include a ground contact 32, which may also be in the form of a spring-loaded carbon brush. In some embodiments the electrical ground contact 32 is in mechanical and electrical communication with the conductive zone 25 to form a current path from the electrical contact 30 to the resistive zone and back to the electrical ground contact 32. As a result, it is created a "heating zone" within the resistive zone 20 that corresponds to the current path through the resistive zone. In this aspect, FIG. 2 illustrates a heating zone 64 that occurs from the flow of current through the resistive zone. The electric current is supplied from the power supply 62 to an electrical contact 30 that is in electrical communication with the conductive zone 25. The electrical contact and the earth contact may have different voltages and may be in electrical communication with a power source AC or DC. Suitable electric brushes include model number RM312A, which are available from Magnetek, Inc.

Although the figures illustrate the presence of a single electrical ground contact 32 for the flow of current back to the source 62, it should be recognized that more than one ground contact can be used to control the current path. In the resistive zone 20, the current will be divided, passing a part through the short path between the electrical contact 30 and the ground contact 32, and the rest taking the long path around the circumference of the resistive zone. If desired, a second ground contact (not shown) may be placed on the opposite side of the electrical contact 30 to prevent unwanted movement of current around the circumference. However, it should be recognized that in some cases the amount of current that takes the longest path should be minimal.

The electrical contact 30 may be arranged in a stationary position with respect to the rotation of the sealant by rotary pulse 10. When the roll rotates, current is applied to the electrically conductive zone and passes to a section of the electrically resistive zone that is in communication electrical with the conductive zone to produce a hot zone. Continuous rotation of the roller rotates the heated part of the electrically resistive member out of the electrical communication with the electrical contact 30 and thus out of the hot zone. The size of the hot zone can be increased or decreased by changing the position of the electrical contact to ground 32 with respect to the position of the electrical contact 30, and vice versa. The greater the distance between the electrical contact and the ground contact, the greater the hot zone.

When materials that can be heat sealed move over the hot zone, the materials melt and melt together to form a heat seal. After passing through the hot zone the heat-sealed materials continue for the roll to keep them for a short distance. During this time the newly formed seal can be cooled properly to form a strong seal that should not break or separate prematurely. If desired, the electric current can be turned on or off to produce a discontinuous seal.

In some cases, the electrically resistive and conductive zones may comprise separate members that are electrically connected, or electrically resistive and conductive members disposed on a single continuous surface or roll.

With reference to FIGS. 3-5, rotary pulse sealants having separate electrically resistive members and separate electrically conductive members are illustrated. FIGS. 3 and 4 illustrate an example in which the resistive member 20 and the conductive member 25 are in electrical communication by means of electrical connectors 35. The electrical connectors 35 form an electrical path between the conductive member and the resistive member. In one example the electrical connectors are formed from cables, conductive inks, conductive pastes, conductive resins, copper plating, metal strips, or equivalent substitutes. The electrical connectors 35 may be attached to the conductive member 25 in a wide variety of ways including, but not limited to, welds, screws, snap hooks, or the like.

The electrically conductive member 25 may comprise a plurality of conductive strips that extend laterally across its surface that are typically isolated from each other. As shown in FIG. 3, the conductive strips, which collectively are referred to with the reference number 50 may comprise active strips 52 and inactive strips 55. The active strips 52 are in electrical communication with the resistive member by means of electrical connectors 35. The inactive strips help to maintain a substantially flat surface for electrical contact when moving on the surface of the conductive member. In an alternative embodiment, the inactive strips may comprise an electrically insulating material, such as polymeric or ceramic compositions, that fills the space between each successive active strip.

The conductive strips may comprise conductive materials that include, but are not limited to, copper, copper alloys, graphite, conductive epoxies, conductive inks, and the like. Typically, conductive strips have minimal or low electrical resistance. In most embodiments, the resistivity of the conductive strips may be less than the resistivity of the resistive material. In one example, a commercially available switch can be used as the conductive member. A switch is a device that can be shaped like a cylinder and has a plurality of individually insulated conductive strips. In some examples, the conductive strips may comprise conductive inks or resins that can be coated or printed on the surface of the conductive member.

With reference to FIGS. 3 and 4, the electrically resistive member 20 comprises a generally cylindrical disk having an electrically resistive material disposed on its surface. The surface 70 of the resistive member 20 comprises a material that electrically and thermally insulates the resistive material from the rest of the resistive member. The resistive material may comprise a resistive band 40 that encompasses the circumference of the resistive member. Although the general shape of the resistive member is normally cylindrical, it should be recognized that other shapes such as a square, hexagon, or octagon can be used.

The resistive band 40 may also include small projections or tabs 47 of resistive material extending outwardly along the surface 70 to contact and overlap the conductive tabs 45. The conductive tabs 45 provide a current path between the electrical connectors 35 and the resistive band 40. In the embodiment illustrated in FIGS. 3 and 4, the electrical connectors are attached to the resistive member by means of conductive tabs 45. Current flows from the electrical connectors 35 through the conductive tabs 45 and to the resistive tabs 47 and then travels to the resistive band 40. The tabs Resistors 47 can help prevent unwanted current flow to the electrical conductive tabs 45 that are disposed between the electrical contact and the ground contact. The conductive tabs 45 may comprise a variety of different materials that are electrically conductive and have a low resistance, such as copper, conductive epoxies, conductive inks, and the like. The conductive tabs 45 may be attached to the surface 70 in a wide variety of ways including, for example, with an adhesive, printing methods, welding, and the like. The electrical connectors 35 may be attached to the conductive tabs 45 in a wide variety of ways including, but not limited to, welds, pressure hooks, clamp fasteners, plating, or the like.

A variety of different materials can be used such as the resistive material including, but not limited to, metal alloys such as nichrome, molybdenum, aluminum chrome iron, MOSi2, thick and thin resistive layers including inks, pastes and resist resins. Resistor inks and resins are particularly useful in the practice of the invention. Resistor inks are well known in the field of electronic devices. Resistor inks can be applied by screen printing, mimeography or any other technique capable of depositing a controlled amount of ink on the surface of the resistive member. Resist tubs are particularly useful because they can be printed on a surface in the desired patterns, and can then be fired to form part of the surface. Additional benefits of resistor inks include the fact that they are capable of being applied in relatively thin layers, for example, of a thickness of about 0.05 mm to 0.04 mm; the low mass that results in rapid heating and low thermal expansion; and the ability to withstand high temperatures. Resistor inks and resins are also useful because they allow a simple method of manufacturing resistive material on the surface of the resistive member. A suitable resistor ink is ESL 3100 Series available at Electro-Science Laboratories.

Resistor inks can be in the form of an emulsion that can be printed or sprayed directly onto the surface, or a thick paste covering the surface 70 of the resistive member 20. The resistor inks typically comprise a glass frit, high resistivity oxide particles such as ruthenium oxide, and an organic vehicle. Resistor inks can be specially formulated so that the final triggered composition has a predetermined resistivity or a preselected resistance temperature coefficient. The resistance temperature coefficient is defined by the amount of resistance change of a material for a given change in temperature.

In some examples, the resistive material may comprise a release agent or a coating that can be applied to the surface of the material, or that can be incorporated into the resistive material itself. Inks, pastes or resist resins may also comprise ceramic materials and / or release agents that can help prevent heat sealable materials from sticking or adhering to the surface of the resistive strip

40. As a result, the rupture or separation of the seal can be substantially reduced. In embodiments where a metal alloy such as nichrome is used as the resistive material, it may be necessary to apply a release or coating agent such as Teflon, silicone, or a glass coating to prevent unwanted adhesion of the material that can be sealed with heat to the resistive element. In examples designed to melt together materials that can be sealed with conductive heat, such as a metallized layer or a poly-coated aluminum sheet, the resistive material may also comprise a non-conductive insulating material such as a protective glass layer or a similar material. In these examples it may also be desirable to cover the conductive member and / or the electrical connectors with a non-conductive insulating material.

It should be recognized that the resistivity of the resistive material depends on many factors such as the thickness of the resistive material, the current, the composition and the like. In addition, it should also be recognized that a resistive material can be selected based on its resistivity and the particular application of its future use. The resistance temperature coefficient (CTR) of the resistive material can be used as a means to actively or passively control the temperature of the heating zone. Depending on the future use of the application, the resistive material can be chosen to have a desired CTR.

The surface 70 of the resistive member typically comprises a material that thermally and electrically insulates the resistive material. The surface 70 may comprise an outer surface layer having a thickness that typically extends beyond the length of the conductive tongues 45, or alternatively, may comprise a coating adhered to the resistive member. Ceramic materials are particularly useful due to their ability as electrical and thermal insulators. A particularly useful ceramic material is Macor®, which is available from Corning Inc., of Corning, NY. Cordierite is another material that can be useful as a surface material.

In an alternative example, the resistive member 20 and the conductive member 25 may be arranged in intimate contact with each other without the use of electrical connectors 35. In this aspect, FIGS. 5a-5c illustrate a side perspective of a resistive member and a conductive member that have been placed in close proximity to each other. FIG. 5a is a lateral perspective of the conductive member. FIG. 5b is a side perspective of the resistive element illustrating the conductive tabs 45 extending downward from the surface of the outer circumference. FIG. 5c is an illustration representing the resistive member 20 and the conductive member aligned with respect to each other. The active conductive strips 52 are aligned with, and in electrical communication with the conductive tab 45 on the resistive member. As a result, the current can flow directly from the conductive member to the resistive member. Typically a crossbow or other mechanism can be used to apply pressure to the conductive and resistive member to maintain electrical contact between the members.

As discussed above, the rotary pulse sealant in some examples may also comprise a continuous surface having a resistive zone and a conductive zone disposed thereon. Similar to the previously described embodiments, the rotary pulse sealant having a continuous surface may have a resistive band comprising a resistive material that is in electrical communication with a plurality of conductive strips.

The size and general orientation of the conductive member with respect to the resistive member may vary depending on the design preference. In some embodiments, the conductive zone may have a diameter that is the same or larger than that of the resistive member. Furthermore, in some embodiments the orientation of the conductive zone with respect to the position of the heat sealable material can be changed 180 degrees so that the heat sealable material can pass over the conductive member when actuated around the resistive member. . In this embodiment, it may be useful to place the electrical contact and the earth contact 180 degrees apart from the vertex of the movement of the material that can be heat sealed around the roll. It should be noted that the positions of the electrical contact and the ground contact do not have to be aligned with the activated conductive strips and may be offset so that the contacts do not interfere with the movement of the heat-sealable material around the roll. The diameter and width of the resistive member may also vary depending on the particular sealing application. For example, the width of the resistive member can be increased to provide a larger heat seal. The shape of the conductive member and the resistive member may vary individually or together. Typically, the roll has a generally cylindrical shape. However, in some embodiments the roll as a whole, or its individual members, may have other shapes such as, for example, a square, hexagon, or octagon.

The rotary pulse sealant may be driven by a motor or by a product. With reference to FIGS. 3 and 4, a device driven by a motor is illustrated. The rotary pulse sealant may also comprise an axis 105 around which the resistive member 20 and the conductive member 25 are disposed. The resistive members and conductive members individually have a runner 100 through which the axis 105 can be inserted. Retaining rings or other fastening devices can be used to positionally secure the resistive and conductive members on the shaft. A rotary pulse sealant driven by a motor typically includes a pulley 125 or sprocket that is in mechanical communication with a motor (not shown). As shown in FIG. 4, the pulley 125 may include a central runner 129 to receive the shaft 105. The central runner may contain a groove 127 for securely engaging the shaft so that the rotation of the pulley can also rotate the shaft. The pulley can be positionally secured to the shaft in a variety of different ways including, for example, retaining rings, stud screws, bolts, and the like.

The resistive and conductive members are normally rotatably fixed or secured to the axis 105 so that the axis will also rotate the resistive member 20 and the conductive members 25. The resistive and conductive members and the axis can be adjusted in a single position (see 115 and 110) so that the rotation of the resistive and conductive members is fixed relative to the axis. FIG. 4 illustrates that shaft 105 may include a key

110. A corresponding slot 115 is shown to receive the key in a fixed manner when it is present in the central passage 100 through which the axis 105 can be inserted. As a result, the rotation of the axis also rotates the resistive and conductive members. It should be recognized that the type of key used and its placement could vary depending on the particular preference of the designer, and that other methods could be used to rotatably fix the resistive and conductive members to the shaft.

In other examples, the movement of heat sealable material on the roll can be used to rotate the conductive and resistive members. In one example, the shaft and the resistive and conductive members can be rotatable around one or more free bearings so that the movement on the roller rotates the entire assembly. In another example, the shaft can be stationary and the movement of heat sealable material over the rotary pulse sealant 10 can be used to rotate the resistive member 20 and the conductive member 25. In this example, the central runner 100 typically It includes one or more friction reducing members that allow members 20, 25 to freely rotate around the shaft in the direction of movement of the heat sealable material. Friction reducing members include bearings such as a free bearing. The bearings may comprise a wide variety of materials including, but not limited to, stainless steel, ceramics, aluminum, plastic, metal alloys such as bronze, and the like. It should be recognized that other methods such as packaged grease could be used, for example, to facilitate rotation of the resistive member and the conductive member about the axis, although not necessarily with equivalent results.

The rotary pulse sealant can also be used together with a pressure belt. In this aspect, FIG. 6 illustrates a pressure belt 150 for maintaining the sealing pressure between two sheets of heat sealable material and the heated surface of the sealant. The pressure belt typically comprises an elastic material that is capable of withstanding high temperatures that the heating zone can generate. In some examples, the belt also includes a release or coating agent, such as Teflon or silicone, to reduce the adhesion of the material that can be sealed to the belt. Pulleys 152, 154, 156 work together to drive belt 150 in the same direction in which the heat-sealing material is moving. In an alternative example, one or more pressure rolls may be used to apply sealing pressure to the material that can be heat sealed when moving over the heating zone. In this example, a first pressure roll could be arranged adjacent to the point at which the heat-sealable material contacts the heating zone and a second pressure roll could be arranged adjacent to the point at which the material that can sealing with heat leaves the heating zone.

In one embodiment, the rotary pulse sealant can also be used to make transverse heat seals. With reference to FIG. 7, a rotary pulse sealant for making transverse seals is illustrated and is generally referred to as reference number 200. The transverse rotary pulse sealant comprises a resistive zone 220 (resistive member) disposed between two electrically conductive zones 225 (conductive members) ). The resistive member 220 comprises a plurality of resistive strips 240 that are thermally and electrically isolated from the roll 200 and with respect to each other. The current supplied from the power supply 262 passes through the electrical contact 230 and returns through the ground contact 232. The current passes through the electrical contact 230 to the conductive strips 252 and through the electrical connectors 235 and to the strips electrically resistive 240 that extend transversely across the surface of the electrically resistive zone (resistive member). When the current passes through the resistive member, the resistive material 240 is heated to create a heating zone. The resistive strip 264 represents a heated strip to produce a transverse heat seal. The resistive member 220 may include conductive tabs 247 for joining the electrical connectors 235. It should be recognized that the conductive members and the resistive member could also be arranged on a continuous roll or directly attached to each other.

The width and distance between the transverse heat seals can be controlled and adjusted by changing various parameters associated with the heat seals. For example, the space between the heat seals can be changed by increasing or decreasing the amount of resistive strips 240 that are disposed on the resistive member. In addition, the current can also be turned on or off for a certain period of time when the material that can be sealed with heat continues to advance. As a result, a predetermined amount of material that can be heat sealed advances without creating a heat seal. The width of the heat seal can increase or decrease by altering the size of the brushes, resistive strips, or a combination of both.

During operation, the amount of heat produced by the resistive zone typically depends on the resistance of the particular resistive material used and the amount of current applied to the device. As such, it should be obvious that the degree of fusion or amount of heat applied to heat sealable materials can be controlled by varying the amount of current applied to the sealant by rotary pulse. For example, for thicker materials it may be necessary to increase the current level so that the resistive zone produces enough heat to melt and melt the materials together. In the same way, the current level could also be used to vary the strength of the seal. Alternatively, the degree of melting can also be controlled by changing the contact time during which heat sealable materials are exposed to the hot zone.

Claims (11)

one.

 A transverse rotary pulse sealant (200) comprising:

a) first and second rotating cylindrical conductive members (225) each having a plurality of electrically conductive strips (252) extending laterally across the surface of said conductive members; b) a rotating cylindrical resistive member (220) disposed between said first and second conductive members (225), said resistive member having a heating zone, cooling zone, an insulated surface and a plurality of electrically resistive strips (240) which is they extend laterally through the surface of said resistive member, wherein said resistive strips are in electrical communication with said first and second conductive members; and c) an electrical contact (230) in electrical communication with said first conductive member and a ground contact (232) in electrical communication with said second conductive member, wherein said heating zone (264) is defined by the current flow from said electrical contact to said earth contact.

2.

 A transverse rotary pulse sealant (200) according to claim 1, further comprising a driven shaft around which said resistive member and said first and second conductive members are arranged.

3.

 A transverse rotary pulse sealant according to claim 2, further comprising a pulley for rotationally actuating said resistive member and said conductive members by means of said axis.

Four.

 A transverse rotary pulse sealant according to claim 1, 2 or 3, wherein said conductive strips comprise copper, conductive epoxies, graphite, or conductive inks.

5.

 A transverse rotary pulse sealant according to any one of claims 1-4, wherein said insulated surface comprises ceramic.

6.

 A transverse rotary pulse sealant according to any one of claims 1-5, wherein said resistive strips comprise nichrome, molybdenum, chromium iron, aluminum, MoSi2, resist inks, resist pastes, or resist resins.

7.

 A transverse rotary pulse sealant according to any one of the preceding claims, wherein the electrical contact comprises a carbon brush in electrical communication with a power source.

8.

 A transverse rotary pulse sealant according to any one of the preceding claims, further comprising a pressure belt disposed adjacent said resistive zone, whereby said pressure belt applies sealing pressure to the material that can be heat sealed by moving between said belt and said resistive zone.

9.

 The use of the transverse rotary impulse seal roll according to any one of the preceding claims.

10.

 A method for making a heat seal comprising:

to.

 providing a transverse rotary pulse sealant according to claim 1;

b.

 apply current to said electrical contact;

C.

pass heat-sealing materials that are in contact face to face on the surface of the heating zone to produce a heat seal; Y

d.

 keep such materials that can be heat sealed in a cooling zone.

11. A method according to claim 10, further comprising the step of turning the current on and off to produce a discontinuous heat seal.